#2 Attitude problems
Aubameyang is, to put it kindly, completely crazy. While his performances on the field are surprisingly almost unaffected by his attitude, you would think it's only a matter of time until they are. However, even if he performs well on the pitch, he is still a handful to deal with and will most likely cause Arsenal problems just like he did at Dortmund.
The striker has been banned by his last three managers during his time at Dortmund. While his most recent suspension can be related to him wanting to force his move to Arsenal, he has been known to skip training occasionally and to take unauthorized trips during his free time.
Aubameyang's mannerisms are easily analyzed, if he's unhappy he lets everyone on the planet know about it and in times where Arsenal really need stability surrounding the club, they are bringing in somebody really doesn't contribute to that.
Like with many of the world's best players, Aubameyang's genius is closely connected to his eccentricity and the Gunners would be ill-advised to try and change him in that regard, despite the fact that they would probably fail in doing so anyway. Nevertheless, the enfant terrible will certainly bring problems with him.